1. Field of the Invention
The present invention relates to interconnections used in the manufacturing of electronic circuit boards, and more specifically, to jumpers used in said manufacture.
2. Description Relative to the Prior Art
Designers of electronic circuits are forever striving to reduce the size of electronic assemblies through miniaturization of the electronic components and maximize space utilization.
The assembly of high-speed memory modules requires the grouping of integrated circuit packages in a closely-interconnected configuration. The packaging configuration must be flexible enough to allow expansion of the memory capacity by addition or substitution of components where the space unused in a low memory capacity system must be balanced against the memory expanding capability.
There is a need for an improved packaging technique that would provide for the convenient expansion of the memory module without requiring a large space allocation in the basic configuration of the module. Such modules are assembled with rigid printed circuit hoards and the flexible jumpers described herein.
The principal objective of this invention are to provide an interconnecting packaging technique for assembling rigid memory modules in a compact arrangement that do not require substantial space allocation for the interconnection of the rigid boards and, at the same time, provide short line lengths, high speed, high reliability and short radius with a 180 degree rotation without subjecting the printed wire conductors to breakage.
This is achieved by combining a number of printed circuit wires on both sides of an insulating substrate such as KAPTON. This layered arrangement of printed wires on both sides of the insolating substrate has each printed wire terminating to a set of combs by means of pads on each side of the wire. Said pads are arranged in a form of mirrored position so that a hole or via is drilled through both corresponding pads. Said via is plated through to provide electrical connection between the upper and lower corresponding pads. Said pads are plated to allow soldered connection to pads of rigid circuit boards.
This general method of connection of multiple circuit boards onto a mother board using a single edge connector is well known in the art, and is the subject of U.S. Pat. No. 5,949,657, issued to Chris Karabatsos, the inventor of the current invention.
The prior art may be understood by referring to FIGS. 6, 7, 8, and 9. FIG. 6 shows a perspective view of two circuit boards, 101 and 102, wherein circuit board 101 contains a comb of contacts 107 which are matingly inserted into one of the edge connectors 8. Referring to FIG. 8, which shows a cross section view of the front assembly shown in FIG. 6, the contacts 107 are shown inserted into the edge connector 8. Also shown in FIG. 8, the jumper assembly 106 is shown.
Referring now to FIG. 7, the two circuit boards 101 and 102 are shown at an early stage of manufacture. The prior art jumper assembly 106, as shown in plan view in FIG. 9, is attached with its upper pads 104 soldered to pads on circuit board 101, and with its lower pads 105 attached to lower board 102. The lower board is then rotated anti-clockwise, in the direction indicated by R in FIG. 7, thus causing the jumper assembly 106 to assume the shape shown in FIG. 8.
The difference between the current invention, and the prior art described in U.S. Pat. No. 5,949,657, is only related to the construction of the jumper assembly. The method of use of the current jumper assembly is identical to that of the prior art jumper assembly described above.
The current invention solves this problem by providing a jumper assembly with a central insulator sheet, and an array of wires or fingers on each face of the central insulator. The array on the top face of the central insulator is the mirror image of the array of wires on the bottom face, except for the length of the pads. The pads are asymmetrical with respect to adjacent pads from the mirror image array. As a result, the points of maximum stress from one array do not align with the points of maximum stress from the facing array.
It is a general object of the present invention to provide a jumper which is flexible, but still has superior mechanical strength. It is a further object of the present invention to provide such a jumper which provides a superior electrical connection as well.
In accordance with one aspect of the invention, a jumper assembly for use in interconnecting electronic components includes a central insulation sheet having an upper side and a lower side, and a first and second set of printed wires, each of which has a multiplicity of foil fingers, spaced from each other, each finger having a top side, a bottom side, and two ends. Each such finger further includes a central area, a major pad, having a length, integrally affixed to one end of the finger, and a minor pad, having a length different than that of the major pad, and integrally affixed to the other end of the finger. The first set of printed wires are bonded at the bottom side to the upper side of the insulation sheet, and the second set of printed wires are bonded at the top side to the lower side of the insulation sheet, so that the major pads of one set of printed wires are adjacent to the minor pads of the other set of printed wires. A first external insulation sheet is bonded to the top side of the first set of printed wires, while a second external insulation sheet is bonded to the bottom side of the second set of printed wires.
In accordance with a second aspect of the invention, a plated-through hole is formed in each pad.
In accordance with a third aspect of the invention, each pad has a facing pad disposed on the opposite side of the central insulation sheet, and a solder connection connects the plated-through holes between each pad and the facing pad.
In accordance with a fourth aspect of the invention, the printed wires are formed of copper foil.
In accordance with a fifth aspect of the invention, the central insulation sheet, and the first and second external insulation sheets are flexible insulators.
In accordance with a sixth aspect of the invention, the insulation sheets are made of KAPTON.
In accordance with a final aspect of the invention, the solder connections between each pad and the facing pad are reflow-soldered connections.